Hi Philip. I'm shorter (5'6"), but also seem to be smack between two bike sizes. Yes, there's a lot of logic to sizing up or down based on application. For example, I make my choice of the bigger or smaller size based on bike geometry and how aggressive I want my ride. Aggressive geometry plus the smaller size is really aggressive. If I want to relax that, I go bigger. Or if the bike is somewhat relaxed geometry and I want to spice it up, I go smaller. In either case, tweaking bike fit (including saddle height and position and stem length) make it work.